This invention relates to a color copier for forming a latent image by color-analyzed light reflected from an original to be copied and forming a toner image by using toner of complementary colors of the color-analyzed light such that color corrections can be effected on the image to be produced.
With the recent development in electrophotography, color copiers capable of forming full-color images are coming to be developed. A color copier is typically comprised of color filters for spectroscopically separating a reflected beam of light from an original into blue, green and red beams and three developing devices having respectively toner of their complimentary colors, that is, yellow, magenta and cyanic and forms a full-color image by three image-forming processes. In other words, a yellow toner image is formed by blue light, a magenta toner image by green light, a cyanic toner image by red light and these three toner images are superposed on a single sheet of paper to form a full-color imaqe.
In the case of an original which is particularly colored, however, exposure, charging voltage of the photoreceptor and/or bias voltage for the developing device must be adjusted every time a toner image is formed such that this particular color can be emphasized. If the original has a strongly reddish image, for example, the cyanic toner image must be made lighter such that red can be emphasized in the copy and for this purpose, exposure must be increased, charging voltage of the photoreceptor must be set close to zero and/or bias voltage of the developing device must be set close to the voltage of the photoreceptor when the cyanic toner image is formed. Such adjustments have conventionally been done manually by the operator. In other words, the operator had to test several times by varying exposure, etc. to determine a desired setting. It is not only time-consuming but also wasteful.